CLINICOPATHOLOGICAL CORRELATION IN ERYTHEMA MULTIFORME AND STEVENS-JOHNSON SYNDROME

Background and Design: To confirm the recent hypothesis that the spect rum of severe erythema multiforme (EM) is actually composed of two dif ferent disorders, we retrospectively studied 38 such cases, particular ly in regard to their histopathologic features. Based on photographs a nd a recent proposal, the cases were classified as EM major when the e ruption consisted of typical or raised atypical target lesions located on the extremities and/or the face or as Stevens-Johnson syndrome whe n the eruption consisted of flat atypical target lesions or purpuric m acules that were widespread or distributed on the trunk. The cases wer e also assessed for causal agent. A biopsy specimen was obtained in ea ch case. Several histologic parameters were analyzed (and scored) with out clinical data and correlated to the clinical pattern. These parame ters were first studied in a global assessment and then in a detailed evaluation. Results: The global assessment showed two different histol ogic patterns: (1) a predominantly inflammatory pattern characterized by a lichenoid infiltrate and epidermal necrosis that mainly affected the basal layer; and (2) a predominantly necrotic pattern in which maj or epidermal necrosis and minimal inflammatory infiltration were found . The former pattern was associated with EM major, the latter with Ste vens-Johnson syndrome (P < .001) and with drug-related cause (P < .001 ). The detailed evaluation showed also less epidermal necrosis, more d ermal inflammation, and more exocytosis in EM major. Conversely, there was more epidermal necrosis, less dermal inflammation, and less exocy tosis in Stevens-Johnson syndrome. The difference was statistically si gnificant for the inflammation and exocytosis. Conclusions: This study suggests that the two different symptomatologies in the spectrum of s evere EM correlate with two different patterns of histopathologic chan ges. A prospective multicentered study should be conducted to definiti vely characterize these entities.